Russians Find Explosives On 2nd Plane

Investigators found traces of explosives on the second of two passenger airliners that crashed simultaneously in Russia, security officials announced Saturday, confirming that they consider the twin air disasters to be terrorist acts.

Facing a menacing turn in Russia's fight against terrorism and eager to calm travelers, the officials announced that they would increase security at the country's airports. The new measures included having Interior Ministry officers screen passengers, starting immediately, and installing sensors able to detect the presence of explosives.

Sergei N. Ignatchenko, chief spokesman of the Federal Security Service, told news agencies that the explosive hexogen was discovered in the wreckage of Volga-AviaExpress Flight 1303, which crashed on Tuesday night outside a village near Tula, about 100 miles south of Moscow.

On Friday, investigators said they had found traces of the same explosive at the site near Rostov-on-Don where Sibir Airlines Flight 1047 crashed within minutes of Flight 1303.

Both planes took off from Domodedovo International Airport, southwest of Moscow, with Flight 1047 headed to Sochi, on the Black Sea, and Flight 1303 to Volgograd.

Investigators searching the wreckage of Flight 1303 also said they had found the remains of a 44th passenger, possibly that of a suicide bomber. That raised the death toll to 90 in Russia's worst act of air terrorism.

The officials said nothing new on Saturday about the investigation. On Friday, the Web site of an Islamic extremist group, the Islamouli Brigades of Al Qaeda, said its fighters had hijacked the airliners to avenge the deaths of Muslims in Chechnya.

Investigators have reportedly focused attention on two passengers -- both women, apparently from Chechnya -- who bought tickets for the flights shortly before departure. Izvestia reported that one of the women, who registered for Flight 1303 as Amanta Nagayeva, 27, was born in the Chechen village of Kirov-Urt.

The newspaper quoted the village's administrator, Dogman Akhmadova, as saying that one of Ms. Nagayeva's three brothers had been seized by Russian forces three or four years ago and never seen again.

A version of this article appears in print on , Section 1, Page 4 of the National edition with the headline: Russians Find Explosives On 2nd Plane. Order Reprints | Today’s Paper | Subscribe